Chromium interlayer amorphous carbon film for 304 stainless steel bipolar plate of proton exchange membrane fuel cell

•Cr/a-C film was prepared for 304SS bipolar plate of PEMFC.•The corrosion resistance and current conductivity are greatly improved.•The assembled Cr/a-C 304SS PEMFC shows better performance and stability.

Excellent electrical conductivity and corrosion resistance make the graphite-like carbon film an ideal surface modification for metal bipolar plates, but the pinhole inside amorphous carbon (a-C) causes pitting corrosion of the substrate. Chromium interlayer amorphous carbon (Cr/a-C) was prepared for 304SS bipolar plate. The interlock structure between the Cr interlayer and a-C film prevented corrosive liquid from reaching the substrate. The Cr/a-C film was prepared on 304SS by direct current magnetron sputtering. The hydrophobic property, interfacial contact resistance (ICR), and corrosion resistance of Cr/a-C 304SS were investigated and compared with those of bare 304SS and a-C 304SS. In addition, the performance and stability of the assembled single fuel cell were analyzed. Results show that the contact angle with water of Cr/a-C 304SS is 89.5°. The ICR of Cr/a-C 304SS under compaction force of 150 N/cm2 is 16.65 mΩ cm2, which is better than that of a-C 304SS. The SEM and TEM results reveal the interlock structure between the Cr interlayer and a-C film. This structure results in excellent corrosion resistance, corrosion potential of − 0.32 V, and corrosion current density of 0.894 μA cm− 2 in the simulated proton exchange membrane fuel cell (PEMFC). Single cell tests show that the peak power density of Cr/a-C 304SS PEMFC is 1.123 W cm− 2, with no observed degradation during 12 h lifetime tests. Thus, the Cr/a-C film is an ideal protective layer for 304SS bipolar plates of PEMFC.